_____________________
                                                         |    OMB APPROVAL     |
                                                         |_____________________|
                                                         |OMB NUMBER: 3235-0145|
                    UNITED STATES                        |EXPIRES:             |
         SECURITIES AND EXCHANGE COMMISSION              |  DECEMBER 31, 2005  |
               Washington, D.C.  20549                   |ESTIMATED AVERAGE    |
                                                         |BURDEN HOURS         |
                                                         |PER RESPONSE ...11   |
                                                         |_____________________|

                                  SCHEDULE 13D

                    Under the Securities Exchange Act of 1934

                               (Amendment No.___)*

                             MERCATOR SOFTWARE, INC.
          ------------------------------------------------------------
                                (Name of Issuer)

                     Common Stock, par value $.01 per share
          -------------------------------------------------------------
                         (Title of Class and Securities)

                                    587587106
          ------------------------------------------------------------
                                 (CUSIP Number)

                         Ascential Software Corporation
                               Attn: Peter Gyenes
                             Chief Executive Officer
                              50 Washington Street
                        Westborough, Massachusetts 01581
                                 (508) 366-3888

                                 With a copy to:

           Scott N. Semel                      Louis A. Goodman, Esq.
   Ascential Software Corporation     Skadden, Arps, Slate, Meagher & Flom LLP
        50 Washington Street                     One Beacon Street
       Westborough, MA  01581                    Boston, MA  02108
           (508) 366-3880                          (617)573-4800
          ------------------------------------------------------------
            (Name, Address and Telephone Number of Person Authorized
                     to Receive Notices and Communications)


                                 August 2, 2003
          ------------------------------------------------------------
             (Date of Event which Requires Filing of this Statement)



If the filing person has previously filed a statement on Schedule 13G to report
the acquisition that is the subject of this Schedule 13D, and is filing this
schedule because of Sections 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check
the following box. [ ]

Note: Schedules filed in paper format shall include a signed original and five
copies of the schedule, including all exhibits. See Section 240.13d-7 for other
parties to whom copies are to be sent.

* The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).


                         (Continued on following pages)




                                  SCHEDULE 13D

CUSIP No. 0001063167
--------------------------------------------------------------------------------
1.    NAMES OF REPORTING PERSON

      Ascential Software Corporation

      I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only)

      943011736
--------------------------------------------------------------------------------
2.    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP:
                                                                         (a) ( )
                                                                         (b) ( )
--------------------------------------------------------------------------------
3.    SEC USE ONLY


--------------------------------------------------------------------------------
4.    SOURCE OF FUNDS*

            WC
--------------------------------------------------------------------------------
5.    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
      TO ITEMS 2(d) or 2(e)                                                  ( )

--------------------------------------------------------------------------------
6.    CITIZENSHIP OR PLACE OF ORGANIZATION

            Delaware
--------------------------------------------------------------------------------
                  7.    SOLE VOTING POWER
    NUMBER OF
                              None
     SHARES       --------------------------------------------------------------
                  8.    SHARED VOTING POWER
  BENEFICIALLY

   OWNED BY                   5,910,134 ((1) and see Item 5)
                  --------------------------------------------------------------
     EACH         9.    SOLE DISPOSITIVE POWER

   REPORTING                  None
                  --------------------------------------------------------------
    PERSON        10.   SHARED DISPOSITIVE POWER

     WITH                     5,910,134 ((1) and see Item 5)
                  --------------------------------------------------------------



11.   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

            5,910,134 ((1) and see Item 5)
--------------------------------------------------------------------------------
12.   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW 11 EXCLUDES CERTAIN SHARES
                                                                             ( )

--------------------------------------------------------------------------------
13.   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11

            15.1%(2)
--------------------------------------------------------------------------------
14.   TYPE OF REPORTING PERSON

            CO
--------------------------------------------------------------------------------

(1)   Based on representations made by the tendering stockholders pursuant to
      the Stock Tender Agreement (as defined in Item 4). The actual number of
      shares beneficially owned is all shares owned as of such date or
      thereafter acquired by the stockholders parties to the Stock Tender
      Agreement.

(2)   Based on 35,266,939 shares of common stock of the Issuer outstanding as of
      July 31, 2003, as represented by the Issuer in the Merger Agreement (as
      defined under Item 4 of this Statement), plus 3,802,428 shares issuable
      upon exercise of options subject to the Stock Tender Agreement (as defined
      under Item 4 of this Statement and as represented by the stockholders
      parties thereto).




CUSIP No. 0001063167
--------------------------------------------------------------------------------
1.    NAMES OF REPORTING PERSON

      Greek Acquisition Corporation

      I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only)


--------------------------------------------------------------------------------
2.    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP:
                                                                         (a) ( )
                                                                         (b) ( )

--------------------------------------------------------------------------------
3.    SEC USE ONLY


--------------------------------------------------------------------------------
4.    SOURCE OF FUNDS*

            AF
--------------------------------------------------------------------------------
5.    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
      TO ITEMS 2(d) or 2(e)                                                  ( )

--------------------------------------------------------------------------------
6.    CITIZENSHIP OR PLACE OF ORGANIZATION

            Delaware
--------------------------------------------------------------------------------
                  7.    SOLE VOTING POWER
    NUMBER OF
                              7,049,861 ((1) and see Item 5)
     SHARES       --------------------------------------------------------------
                  8.    SHARED VOTING POWER
  BENEFICIALLY
                              5,910,134 ((1) and see Item 5)
   OWNED BY       --------------------------------------------------------------
                  9.    SOLE DISPOSITIVE POWER
     EACH
                              7,049,861 ((1) and see Item 5)
   REPORTING      --------------------------------------------------------------
                  10.  SHARED DISPOSITIVE POWER
    PERSON
                              5,910,134 ((1) and see Item 5)
     WITH         --------------------------------------------------------------



11.   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

            12,959,995 ((1) and see Item 5)

--------------------------------------------------------------------------------
12.   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW 11 EXCLUDES CERTAIN SHARES
                                                                             ( )

--------------------------------------------------------------------------------
13.   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11

            28.1% (3)
--------------------------------------------------------------------------------
14.   TYPE OF REPORTING PERSON

            CO
--------------------------------------------------------------------------------

(3)   Based on 35,266,939 shares of common stock of the Issuer outstanding as of
      July 31, 2003, as represented by the Issuer in the Merger Agreement (as
      defined under Item 4 of this Statement), plus 7,049,861 shares subject to
      the Stock Option Agreement (as defined under Item 4 of this Statement and
      based on the number of shares outstanding as of July 31, 2003), plus
      3,802,428 shares issuable upon exercise of options subject to the Stock
      Tender Agreement (as defined under Item 4 of this Statement and as
      represented by the stockholders parties thereto).







ITEM 1. SECURITY AND ISSUER.

            The class of equity securities to which this Statement on Schedule
13D (this "Schedule 13D") relates is the common stock, par value $.01 per share
(the "Common Stock"), of Mercator Software, Inc. (the "Issuer"). The principal
executive offices of the Issuer are located at 45 Danbury Road, Wilton,
Connecticut 06897.

ITEM 2. IDENTITY AND BACKGROUND.

            (a) - (c), (f) This Schedule 13D is being filed by Ascential
Software Corporation, a Delaware Corporation ("Parent"), and Greek Acquisition
Corporation, a Delaware corporation and a wholly-owned subsidiary of Parent (the
"Purchaser"). The principal business of Parent is supplying data integration
solutions to organizations worldwide. The Purchaser is a newly-incorporated
corporation formed by Parent solely for the purpose of acquiring ownership of
the Issuer. The address of Parent's and Purchaser's principal executive offices
is 50 Washington Street, Westborough, Massachusetts 01581

            Certain information concerning the executive officers and directors
of Parent and Purchaser is set forth in Schedule A hereto and is incorporated
herein by reference.

            (d) - (e) During the past five years, neither Parent nor Purchaser
nor, to the best knowledge of Parent and Purchaser, any of the directors and
officers of Parent and Purchaser, who are listed on Schedule A hereto, has been
convicted in a criminal proceeding (excluding traffic violations or similar
misdemeanors) or was a party to a civil proceeding of a judicial or
administrative body of competent jurisdiction as a result of which any such
person was or is subject to a judgment, decree or final order enjoining future
violations of, or prohibiting or mandating activities subject to, Federal or
State securities laws or finding any violation with respect to such laws.

ITEM 3. SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.

            The total amount of funds required to purchase all of the shares of
Common Stock of the Issuer issuable pursuant to the Stock Option Agreement (as
defined under Item 4 below and based on the assumption therein) is $21,149,583
of which $70,498.61 is payable in cash and the remainder by note (based on the
number of shares



outstanding as of July 31, 2003). In the event that the Option (as defined under
Item 4 below) is exercised, Parent would provide such funds to Purchaser from
Parent's available cash and working capital.

            The total amount of funds required to purchase all of the shares of
Common Stock of the Issuer (including shares issuable upon the exercise of
options) subject to the Stock Tender Agreement (as defined under Item 4 below)
and subject to the assumptions described therein is $17,730,402. To the extent
that such shares are tendered in accordance with the terms of the Offer (as
defined under Item 4 below), such funds will be included in the aggregate
consideration required to consummate the Offer (as defined under Item 4 below)
and the Merger (as defined under Item 4 below), which funds will be provided by
Parent to Purchaser from Parent's available cash and working capital. To the
extent that such shares are not tendered in accordance with the terms of the
Offer (as defined under Item 4 below), and Parent subsequently exercises its
option under the Stock Tender Agreement (as defined under Item 4 below) to
purchase such shares, Parent will obtain such funds from Parent's available cash
and working capital.

            The total amount of funds required by Parent to consummate the Offer
(as defined under Item 4 below) and the Merger (as defined under Item 4 below)
is estimated to be approximately $106 million plus any related transaction fees
and expenses. Parent will obtain such funds from available cash and working
capital.

ITEM 4. PURPOSE OF THE TRANSACTION.

            (a) - (g) On August 2, 2003, Parent, Purchaser and the Issuer
entered into an Agreement and Plan of Merger (the "Merger Agreement"). Pursuant
to the Merger Agreement, Purchaser commenced an offer to purchase all of the
outstanding Common Stock (together with any associated preferred stock or other
rights issued pursuant to the Rights Agreement, dated as of September 2, 1998,
by and between Issuer and The Bank of New York, as Rights Agent) at a price per
share of $3.00, net to the stockholder in cash (the "Offer Price"), upon the
terms and subject to the conditions set forth in the Offer to Purchase and
related Letter of Transmittal (which together with any amendments or supplements
thereto will constitute the "Offer") sent to Issuer's stockholders on or about
August 8, 2003. The Offer is subject to various conditions, including, among
other things, the receipt of tenders of at least 51% of the outstanding Common
Stock, on a fully diluted basis. Subject to certain exceptions, following
satisfaction or waiver of the conditions of the Offer, Purchaser will purchase
all of the outstanding Common Stock validly tendered pursuant to the Offer and
not withdrawn.




            The Merger Agreement further provides that after purchase of the
Common Stock (together with any associated preferred stock or other rights) by
Purchaser in the Offer, and subject to the satisfaction or waiver of certain
other conditions, Purchaser will be merged with and into the Issuer (the
"Merger"), with the Issuer surviving the merger as the Surviving Corporation and
becoming a wholly-owned subsidiary of Parent. Pursuant to the Merger Agreement,
at the effective time of the Merger each share of Common Stock outstanding
immediately prior to the effective time of the Merger (other than shares held by
Parent or any subsidiary of Parent (including Purchaser), which will all be
cancelled, or by holders who have perfected their dissenters rights under
Delaware law) will be converted into the right to receive the Offer Price,
without interest.

            In connection with the Merger Agreement, Parent, Purchaser and
certain directors, executive officers and officers of the Issuer identified
therein (each an Individual and collectively, the "Individuals") entered into a
Stock Tender Agreement (the "Stock Tender Agreement") dated as of August 2,
2003, which provides for the tender by such Individuals of the shares of Common
Stock held by them as of that date or acquired prior to the consummation or
termination of the Offer (whether by exercise of options or otherwise) (such
shares of Common Stock being referred to as "Issuer Shares") pursuant to the
Offer, the grant by such Individuals of an irrevocable proxy to officers of
Purchaser to vote their Issuer Shares in favor of the Merger and the Merger
Agreement and against any action or agreement that is contrary to the Merger
Agreement and the grant by such Individual to Parent of an option to purchase
such Individual's Issuer Shares in the event such Individual fails to comply
with the terms of the Stock Tender Agreement.

            In connection with the Merger Agreement, Parent, Purchaser and
Issuer entered into a Common Stock Option Agreement (the "Stock Option
Agreement") dated as of August 2, 2003, pursuant to which Issuer granted
Purchaser an option (the "Option") to purchase up to 19.99% of the then
outstanding Issuer Shares at a purchase price per share equal to the Offer Price
if Purchaser has accepted and made payment for the Common Stock validly tendered
and not withdrawn in the Offer and following the exercise of the Option,
Purchaser will own at least 90% of the then outstanding Common Stock.

            The foregoing descriptions of the Merger Agreement, Stock Tender
Agreement and Stock Option Agreement are qualified in their entirety by
reference to the full text of the forms of the Merger Agreement, Stock Tender
Agreement and Stock Option Agreement, which are incorporated herein by
reference. Copies of the Merger Agreement,



the Stock Tender Agreement and the Stock Option Agreement are attached to this
Schedule 13D as Exhibits 1, 2 and 3, respectively.

            (h) - (j) Upon consummation of the Merger as contemplated by the
Merger Agreement, the Common Stock will be delisted from the Nasdaq Stock
Market, and the Common Stock will become eligible for termination of
registration pursuant to Section 12(g)(4) of the Securities Exchange Act of
1934, as amended.

ITEM 5. INTEREST IN THE SECURITIES OF THE ISSUER.

            (a) - (b) Purchaser may be deemed to beneficially own 7,049,861
shares of Common Stock as a result of the execution of the Stock Option
Agreement, and would have sole voting and dispositive power with respect to any
shares issuable to Purchaser upon exercise of the Option. Each of Parent and
Purchaser may be deemed to beneficially own 5,910,134 shares of Common Stock
(including 3,802,420 shares of Common Stock underlying options exercisable
within 60 days of August 2, 2003) as a result of the execution of the Stock
Tender Agreement and based on the representations of the stockholders parties
thereto. Pursuant to the Stock Tender Agreement, the stockholder parties thereto
have agreed to tender their Issuer Shares in accordance with the terms and
conditions of the Offer and to grant Parent an option to acquire such Issuer
Shares if they fail to comply with their obligations under the Stock Option
Agreement. As a result, each of Parent and Purchaser may be deemed to have
voting power and dispositive power with respect to the shares of Common Stock
covered by the Stock Tender Agreement.

            The aggregate number of shares of Common Stock that may be deemed to
be beneficially owned by Parent constitutes approximately 15.1% of the
outstanding shares of Common Stock (based on 35,266,939 shares of Common Stock
outstanding as of July 31, 2003, as represented by the Issuer in the Merger
Agreement, plus 3,802,428 shares of Common Stock issuable upon exercise of
options subject to the Stock Tender Agreement). The aggregate number of shares
of Common Stock that may be deemed to be beneficially owned by Purchaser
constitutes approximately 28% of the outstanding shares of Common Stock (based
on 35,266,939 shares of Common Stock outstanding as of July 31, 2003, as
represented by Issuer in the Merger Agreement, plus 7,049,761 shares of Common
Stock subject to the Stock Option Agreement based on the number of shares
outstanding as of July 31, 2003, plus 3,802,428 shares of Common Stock issuable
upon exercise of options subject to the Stock Tender Agreement as represented by
the stockholder parties thereto).

Parent and Purchaser each disclaims beneficial ownership of the shares



of Common Stock covered by the Stock Option Agreement and the Stock Tender
Agreement.

            (c) Other than as set forth in this Item 5, there have been no
transactions in the shares of Common Stock effected during the past 60 days by
Parent or Purchaser, nor to the knowledge of Parent or Purchaser, as of the date
hereof, by any person listed on Schedule A hereto.

            (d) No other person is known by Parent or Purchaser to have the
right to receive or the power to direct the receipt of dividends from, or the
proceeds from the sale of, the Common Stock obtainable by Parent or Purchaser
upon exercise of the Option or pursuant to the Stock Tender Agreement.

            (e) Not applicable.

ITEM 6. CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT TO
        SECURITIES OF THE ISSUER.

            The information set forth in Items 3, 4 and 5 of this Schedule 13D
and the Exhibits to this Schedule 13D are hereby incorporated by reference
herein.

ITEM 7. MATERIAL TO BE FILED AS EXHIBITS.



   Exhibit No.    Exhibit Name
   -----------    ------------
               
      1           Agreement and Plan of Merger, dated August 2, 2003, by and
                  among Parent, Purchaser and Issuer (incorporated herein by
                  reference to Exhibit 2.1 to Parent's Current Report on Form
                  8-K dated August 2, 2003 filed on August 5, 2003).

      2           Common Stock Option Agreement, dated as of August 2, 2003, by
                  and among Parent, Purchaser and Issuer (incorporated herein
                  by reference to Exhibit 10.2 to Parent's Current Report on
                  Form 8-K dated August 2, 2003 filed on August 5, 2003).

      3           Stock Tender Agreement, dated as of August 2, 2003, by and
                  among Parent, Purchaser and certain stockholders of Issuer
                  (incorporated herein by reference to Exhibit 10.1 to Parent's
                  Current Report on Form 8-K dated August 2, 2003 filed August
                  5, 2003).

      4           Joint Filing Agreement, dated as of August 12, 2003, by and
                  between Parent and Purchaser.




                                   SIGNATURES

            After reasonable inquiry and to the best of my knowledge and belief,
I certify that the information set forth in this Statement is true, complete,
and correct.

Dated: August 12, 2003

                                   ASCENTIAL SOFTWARE CORPORATION

                                   By:  /s/ Peter Gyenes
                                        -----------------------------
                                   Name:  Peter Gyenes
                                   Title: Chief Executive Officer



                                   GREEK ACQUISITION CORPORATION

                                   By:  /s/ Peter Fiore
                                        -----------------------------
                                   Name:  Peter Fiore
                                   Title: President






                                                                      SCHEDULE A

                        DIRECTORS AND EXECUTIVE OFFICERS
                                       OF
                         ASCENTIAL SOFTWARE CORPORATION
                                       AND
                          GREEK ACQUISITION CORPORATION

            The following table sets forth the name, business address and
present principal occupation or employment of each director and executive
officer of Ascential Software Corporation. Unless otherwise indicated, each such
person is a citizen of the United States, and the business address of each such
person is c/o Ascential Software Corporation, 50 Washington Street, Westborough,
Massachusetts 01581.

                         ASCENTIAL SOFTWARE CORPORATION



NAME                          PRESENT PRINCIPAL OCCUPATION
                           

Peter Gyenes                  Chairman of the Board of Directors and Chief
                              Executive Officer of Ascential Software
                              Corporation

Peter Fiore                   President of Ascential Software Corporation

Robert C. McBride             Vice President and Chief Financial Officer of
                              Ascential Software Corporation

Scott N. Semel                Vice President, General Counsel and Secretary of
                              Ascential Software Corporation

John J. Gavin                 Director of Ascential Software Corporation

David J. Ellenberger          Director of Ascential Software Corporation and
                              Chief Executive Officer of 170 Systems, Inc.

William J. Weyand             Director of Ascential Software Corporation

Robert M. Morrill             Director of Ascential Software Corporation and
                              general partner of Morrill Associates, L.P.





            The following table sets forth the name, business address and
present principal occupation or employment of each director and executive
officer of Greek Acquisition Corporation. Unless otherwise indicated, each such
person is a citizen of the United States, and the business address of each such
person is c/o Ascential Software Corporation, 50 Washington Street, Westborough,
Massachusetts 01581.

                          GREEK ACQUISITION CORPORATION



NAME                          PRESENT PRINCIPAL OCCUPATION
                           

Peter Fiore                   President of Ascential Software Corporation AND
                              President and Director of Greek Acquisition
                              Corporation

Robert C. McBride             Vice President and Chief Financial Officer of
                              Ascential Software Corporation AND Treasurer and
                              Director of Greek Acquisition Corporation

Scott N. Semel                Vice President, General Counsel and Secretary of
                              Ascential Software Corporation AND Secretary and
                              Director of Greek Acquisition Corporation




                                  EXHIBIT INDEX



  Exhibit No.     Exhibit Name
  -----------     ------------
               

      1           Agreement and Plan of Merger, dated August 2, 2003, by and
                  among Parent, Purchaser and Issuer (incorporated herein by
                  reference to Exhibit 2.1 to Parent's Current Report on Form
                  8-K dated August 2, 2003 filed on August 5, 2003).

      2           Common Stock Option Agreement, dated as of August 2, 2003, by
                  and among Parent, Purchaser and Issuer (incorporated herein
                  by reference to Exhibit 10.2 to Parent's Current Report on
                  Form 8-K dated August 2, 2003 filed on August 5, 2003).

      3           Stock Tender Agreement, dated as of August 2, 2003, by and
                  among Parent, Purchaser and certain stockholders of Issuer
                  (incorporated herein by reference to Exhibit 10.1 to Parent's
                  Current Report on Form 8-K dated August 2, 2003 filed August
                  5, 2003).

      4           Joint Filing Agreement, dated as of August 12, 2003, by and
                  between Parent and Purchaser.